Host ownership should survive disconnects and rejoins

[coder13]

Room creators/hosts should retain or regain host controls when they leave and come back.

Feedback source:

• "Could you make it so that when the person who made the room leaves and comes back, they can still change scramble type and stuff like that."

Acceptance ideas:

• Track original room creator separately from current active leader/host.
• If the creator rejoins, restore creator-only controls where appropriate.
• Avoid leaving rooms unmanageable when the current leader disconnects.
• Define how this interacts with leader transfer and Grand Prix rooms.